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How are brain and spinal cord tumors in adults diagnosed?

Brain and spinal cord tumors are usually found because of signs or symptoms a person is having. If a tumor is suspected, tests will be needed to confirm the diagnosis.

Medical history and physical exam

If signs or symptoms suggest you might have a brain or spinal cord tumor, your doctor will get a complete medical history, focusing on your symptoms and when they began. The doctor will also do a neurologic exam to check your brain and spinal cord function. It tests reflexes, muscle strength, vision, eye and mouth movement, coordination, balance, alertness, and other functions.

If the results of the exam are abnormal, your doctor may refer you to a neurologist (a doctor who specializes in medical treatment of nervous system diseases) or a neurosurgeon(a doctor who specializes in surgical treatment of nervous system diseases), who will do a more detailed neurologic exam or other tests.

Imaging tests

Your doctor may order one or more imaging tests. These tests use x-rays, strong magnets, or radioactive substances to create pictures of the brain and spinal cord. The pictures may be looked at by doctors specializing in this field (neurosurgeons, neurologists, and neuroradiologists) as well as by your primary doctor.

Magnetic resonance imaging (MRI) and computed tomography (CT) scans are used most often for brain diseases. These scans will show a brain tumor, if one is present, in almost all cases. Doctors can often also get an idea about what type of tumor it might be, based on how it looks on the scan and where it is in the brain.

Magnetic resonance imaging (MRI) scan

MRI scans are very good for looking at the brain and spinal cord and are considered the best way to look for tumors in these areas. The images they provide are usually more detailed than those from CT scans (described below). But they do not image the bones of the skull as well as CT scans and therefore may not show the effects of tumors on the skull.

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium may be injected into a vein before the scan to help see details better.

MRI scans can take a long time — often up to an hour. You may have to lie on a table that slides inside a narrow tube, which can be confining and might upset people with a fear of enclosed spaces. Newer, open MRI machines can sometimes be used instead, but they might result in less detailed images and can’t be used in all cases. The machine also makes buzzing and clicking noises that you may find disturbing. Some people might need medicine to help them relax for the test.

Magnetic resonance angiography (MRA): This special form of MRI may be done to look at the blood vessels in the brain. This can be very useful before surgery to help the surgeon plan an operation.

Magnetic resonance spectroscopy (MRS): This test is like an MRI, except that it measures radio wave interactions with different chemicals in the brain. MRS highlights some features of brain tumors that are not clearly seen by MRI. It creates graph-like results called spectra (although basic images can also be created). This might give clues as to the type of tumor, but in most cases a biopsy of the tumor is still needed to get an accurate diagnosis. MRS can also be used after treatment to help determine if an area that still looks abnormal on another test is remaining tumor or if it is more likely to be scar tissue.

Magnetic resonance perfusion: For this test, also known as perfusion MRI, a contrast dye is injected quickly into a vein. A special type of MR image is then obtained to look at the amount of blood going through different parts of the brain and tumor. Tumors often have a bigger blood supply than normal areas of the brain. A faster growing tumor may need more blood.

Perfusion MRI can give doctors an idea of the best place to take a biopsy. It can also be used after treatment to help determine if an area that still looks abnormal is remaining tumor or if it is more likely to be scar tissue.

Functional MRI (fMRI): This newer type of MRI looks for tiny blood flow changes in an active part of the brain. It can be used to determine what part of the brain handles a function such as speech, thought, sensation, or movement. Doctors can use this to determine which parts of the brain to avoid when planning surgery or radiation therapy.

This test is similar to a standard MRI, except that you will be asked to do specific tasks (such as answering simple questions or moving your fingers) while the scans are being done.

Computed tomography (CT) scan

The CT scan is an x-ray test that produces detailed cross-sectional images of your brain and spinal cord (or other parts of the body). Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.

CT scans are not used as often as MRI scans when looking at brain or spinal cord tumors, but they can be useful in some cases. They may be used if MRI is not an option (such as in people who are very overweight or people who have a fear of enclosed spaces). CT scans also show greater detail of the bone structures near the tumor.

Before the scan, you may get an injection of a contrast dye through an IV (intravenous) line. This helps better outline any tumors that are present. The contrast may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, people have more serious reactions like trouble breathing or low blood pressure. Be sure to tell the doctor if you have any allergies or if you ever had a reaction to any contrast material used for x-rays.

A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You need to lie still on the table while the scan is being done. Some people feel a bit confined by the ring while the pictures are being taken, although it is not as narrow as an MRI tube.

CT angiography (CTA): For this test, you are injected with a contrast material through an IV line while you are in the CT scanner. The scan creates detailed images of the blood vessels in the brain, which can help doctors plan surgery. CT angiography can provide better details of the blood vessels in and around a tumor than MR angiography in some cases.

Positron emission tomography (PET) scan

For this test, a radioactive substance (usually a type of sugar known as FDG) is injected into the blood. The amount of radioactivity used is very low and passes out of the body within a day or so. Because tumor cells in the body grow quickly, they absorb larger amounts of the sugar than most other cells. After about an hour, you are moved onto a table in the PET scanner. You lie on the table for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not as detailed as a CT or MRI scan, but it can provide helpful information about whether abnormal areas seen on other tests (such as MRIs) are likely to be tumors or not.

This test is also useful after treatment to help determine if an area that still looks abnormal on an MRI scan is remaining tumor or if it is more likely to be scar tissue. Any remaining tumor will show up on the PET scan, while scar tissue will not.

Chest x-ray

A chest x-ray may be done to look for tumors in the lungs if a tumor is found in the brain, because in adults most tumors in the brain have actually started in another organ (most often the lung) and then spread to the brain. This test can be done in a doctor’s office, in an outpatient radiology center, or in a hospital.

Angiogram

For this test, a special dye is injected into blood vessels near the tumor, and the area is then viewed with x-rays. This helps doctors look at the blood supply of a tumor.

This test is not done much for brain or spinal cord tumors anymore, as it has largely been replaced by other tests that can look at blood vessels, such as computerized tomographic angiography (CTA) or magnetic resonance angiography (MRA).

Rarely, an angiogram may be used as part of the treatment for certain brain tumors. It is done as a first step of a procedure called embolization, in which the radiologist injects tiny particles into the blood vessels feeding the tumor to block them and make it easier to remove the tumor.

Brain or spinal cord tumor biopsy

Imaging tests such as MRI and CT scans may show an abnormal area that is likely to be a brain or spinal cord tumor. But most often these scans can’t tell exactly what type of tumor it is. This can only be done by removing some of the tumor tissue, which is called a biopsy. A biopsy may be done as a procedure on its own, or it may be part of surgery to treat the tumor.

Once the tissue is removed, it is looked at under a microscope by a pathologist (a doctor specializing in diagnosis of diseases by lab tests). Sometimes it might need to be looked at by a neuropathologist, a pathologist who specializes in nervous system diseases. The pathologist determines if the tumor is benign or malignant (cancerous) and exactly what type of tumor it is.

Sometimes, a tumor may look so much like an astrocytoma on an MRI scan that a biopsy is not needed, especially if the tumor is in a part of the brain that would make it hard to biopsy (such as the brain stem). In rare cases a PET scan or MR spectroscopy may give enough information so that a biopsy is not needed.

There are 2 main types of biopsies for brain tumors.

Stereotactic (needle) biopsy

This type of biopsy may be used if, based on imaging tests, the risks of surgery to remove the tumor might be too high (such as with some tumors in vital areas, those deep within the brain, or other tumors that probably can’t be treated with surgery) but a sample is still needed to make a diagnosis.

The patient may be asleep (under general anesthesia) or awake during the biopsy. If the patient is awake, the neurosurgeon injects a local anesthetic into areas of skin above the skull to numb them. (The skull and brain do not feel pain.)

A rigid frame may then be attached to the head. This helps make sure the surgeon is targeting the tumor precisely. An incision (cut) is made in the scalp and a small hole is drilled in the skull. An MRI or CT scan is often used along with the frame to help the neurosurgeon guide a hollow needle into the tumor to remove small pieces of tissue.

Another approach is to get an MRI or CT, use scalp markers or facial and scalp contours to create a map of the inside of the head, and then use an image-guidance system to direct the needle into the tumor. This still requires making an incision and drilling a small hole into the skull.

The removed tissue is sent to a pathologist, who looks at it under a microscope to determine what type of tumor it is. This is very important in determining the prognosis (outlook) and the best course of treatment.

Surgical or open biopsy (craniotomy)

If imaging tests show the tumor can be treated with surgery, the neurosurgeon may not do a needle biopsy. Instead, he or she may do an operation called a craniotomy (described in the “Surgery for adult brain and spinal cord tumors” section) to remove all or most of the tumor. (Removing most of the tumor is known as debulking.)

Small samples of the tumor are looked at right away by the pathologist while the patient is still in the operating room, for a preliminary diagnosis. This can help guide treatment, including whether further surgery should be done at that time. A final diagnosis is made within a few days in most cases.

Lumbar puncture (spinal tap)

This test is used to look for cancer cells in the cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord. For this test, you lay on your side on a bed or exam table with your knees up near your chest. The doctor first numbs an area in the lower part of the back near the spine. A small, hollow needle is then placed between the bones of the spine to withdraw some of the fluid.

This fluid is sent to a lab to be looked at under a microscope for cancer cells. Other tests may be done on the fluid as well.

Lumbar punctures are usually very safe, but doctors have to make sure the test does not result in a large drop in pressure in the fluid, which could possibly cause serious problems. For this reason, imaging tests such as CT or MRI scans are done first.

Lumbar punctures usually aren’t done to diagnose brain tumors, but they may be done to help determine the extent of a tumor by looking for cancer cells in the CSF. They are often used if a tumor has already been diagnosed as a type that can commonly spread through the CSF, such as an ependymoma. Lumbar punctures are particularly important in people with suspected brain lymphomas because often the lymphoma cells spread into the CSF.

Blood and urine tests

These lab tests rarely are part of the actual diagnosis of brain and spinal cord tumors, but they may be done to check how well the liver, kidneys, and some other organs are working. This is especially important before any planned surgery. If you are getting chemotherapy, blood tests will be done routinely to check blood counts and to see if the treatment is affecting other parts of the body.